The present invention relates to an ozone generator and, in particular, to a relatively small and light ozone generating system and method capable of producing ozone with much less consumption of electric power.
Ozone (O3), triatomic form of oxygen, has very strong oxidant properties as it is particularly unstable and tends to reduce to diatomic molecule of oxygen (O2) under the normal temperature and pressure. Common uses for ozone include water or air purification, deodorization and bleaching. A wide variety of methods have been proposed to increase the ozone generation efficiency. The efficiency depends on a number of factors including the reactant gas concentration, electric power applied, temperature and gas flow rate.
An ozone generator produces ozone by applying strong energy into air that contains oxygen (O2). Depending on how the energy is applied, ozone generators are generally classified into two types. The first type of ozone generators use ultraviolet ray while the second type of ozone generators use a high electric field that induces corona discharge in the air. As for the ultraviolet types, it is difficult to make a small and compact ultraviolet ray lamp that generates ultraviolet ray. Additionally, the lamp is fragile and poor in long-time reliability. Corona discharge types perform better because they are energy efficient, stable and easy to control. Therefore, nowadays most of ozone generators are using corona discharge. Corona-discharging ozone generators usually have a pulse generating circuit for generating high voltage pulses that are essential in initiating discharge. They also have a discharge chamber into which air or pure oxygen is supplied and out of which resultant ozone exit.
FIG. 1 illustrates a conventional ozone generating system 100. It is generally comprised of a ground electrode 110, a dielectric layer 120, a high-voltage electrode 130, a high-voltage pulse generator 140 and an AC power source 150. Air is continually supplied into the gap between the grounded electrode 110 and dielectric layer 120 inside a chamber (not shown). When a high voltage is applied between the ground electrode 110 and high-voltage electrode 130, the oxygen in the air oxidizes to become ozone.
In operation, the high-voltage pulse generator 140 receives AC power from the AC source and generates sinusoidal or square wave before amplifying them to a level of 3-20 kV. Thus amplified pulses are applied between the electrodes. The dielectric layer 120 disposed between the two electrodes serves to prevent local arcs and helps to generate uniform plasma over the surface of the electrodes. The high-voltage pulse generator 140 includes a transformer with a high winding ratio in order to get high voltage required for the generation of plasma. One of the problems in using a high winding ratio transformer is an increased size of the transformer, requiring heat dissipation. As a result, power loss is significant.
As an alternative form to the discharge chamber of FIG. 1, tube-type ozone generators with glass or quartz tubular dielectric layer have been proposed and widely used in a large-capacity application. But, the mechanism of generating ozone is similar to that of the previous ozone generators and the overall size of the alternative design ozone generators is still large.
In an ozone generator, a non-negligible portion of input electrical power gets converted to heat energy, raising the temperate of the discharge chamber, and thus lowering the ozone generation efficiency. For at elevated temperatures, ozone reduces back to oxygen much faster. In order to cool the discharge chamber, an air/water cooling device was used, contributing to the increased size and complexity.
Conventionally a dehumidifier has been used in order to supply dry air into the discharge chamber. A humid air causes corrosion of the walls of a discharge chamber because moisture in the humid air reacts with ozone to create nitric acid (HNO3) that shortens the life span of the whole system. Corrosion-resistant stainless steel (e.g. SUS316), which is very expensive, has been used as a material of the chamber walls to combat the corrosion. Any yet it is not permanent and thus requires periodic cleaning or replacement of the discharge chamber. All these attributed to an increase in the production costs.
It is therefore an objective of the present invention to provide a highly efficient and compact ozone generator.
It is another objective of the present invention to provide an ozone generator that has a longer life span as a whole.
It is still yet another objective of the present invention to provide such an ozone generator that can be manufactured with lower cost.
In accordance with one aspect of the present invention, the ozone generator includes LC circuit for compressing square wave signals and generating impulses. The use of impulses greatly reduces the winding ratio of transformer and thus overall volume of ozone generator. Power consumption can be also largely reduced.
In accordance with another aspect of the present invention, the ozone generator comprises electrode plates disposed parallel to the discharge chamber wall and dielectric plates adhered to electrodes. A plurality of electric fields are formed vertically between chamber wall and plates, thereby generating ozone much more power efficiently. According to this aspect of the present invention, the discharge chamber is provided in a flat form. Therefore, it is possible to make the generator extremely compact and air-cooling much easier without an additional cooling system.
In accordance with yet another aspect of the present invention, a sheet of oxide dielectric covers the chamber wall. The oxide dielectric prevents corrosion of chamber wall and eliminates the need of installing a dehumidifier.